| 摘要 |
PURPOSE:To avoid a variation in a motor torque due to the secondary resistance change caused by a temperature rise by maintaining a slip frequency constant when the value divided by an inverter frequency by an inverter input voltage is the prescribed value or higher. CONSTITUTION:An inverter frequency command value (f) and an inverter input voltage Ec obtained from an inverter input voltage detector 17 are input to a divider 21. The divider 21 outputs f/Ec to a current pattern generator 20, and when the value of the f/Ec arrives at the prescribed value, the current command value Ip output from the generator 20 is reduced in the prescribed pattern. The slip frequency of the motor is controlled to maintain substantially constant in an operation range exceeding the predetermined value from the f/Ec by the operation of a current regulator 13 which inputs a deviation between the actual current value and a varying current command value. |
